What is an eating disorder? When does what probably began as healthy weight watching become so extreme it is a disorder? I remember asking a friend years ago, who had been hospitalized for anorexia, how it started. She said it began with less butter on the bread. Then it was less bread. Then it was no bread at all.

What lies at the heart of the disorder is body image. A person's vision of who they want to be becomes so warped that in trying to achieve this vision they are destroying themselves and breaking the hearts of those who love them.

Thin delves into the world of four young women from the ages of 15 to 32, who need extreme treatment for both anorexia and bulimia. There is Shelly, who is 25 and has a degree in nursing. Polly, 31 who graduated with an English Literature degree. Brittany who is 15 and Alisa, 30, who lost her friends and general activities to bulimia. All are checked into Renfrew, a strict and thorough clinic that begins with a gloved baggage check.

The girls are not allowed to bring jackets or bags into the dining room so the staff will know they are eating their food and not stashing it. Shelly has been on a feeding tube for five years. She's been hospitalized multiple times. She's missed her birthday, Christmas and other holidays to being in a clinic or hospital.

Polly celebrates her birthday at Renfrew and eats a cupcake delicately and watchfully. Later her eyes tear up because her throat burns so badly after eating the desert. She looks young for her 31 years despite her dieting addiction and her smoking habit. She and Shelly become friends. They gossip on the "smoke porch," where the rules are different. Calories can be spoken of on the smoke porch. Staff bashing is allowed and is frequently done.

Brittany went from overweight to underweight by losing 88 pounds in a single year. She arrives at Renfrew with liver damage and noticeable hair loss. She will pull at her skin and cry about being fat.

Alisa describes one episode with her disorder. She went to McDonald's then Burger King for breakfast items after buying donuts. She then goes to a supermarket and buys two half gallons of ice cream, whipped cream, pastries, peanut butter and marsh-mellows, She goes home and eats the donuts, the entire dozen of them, then both breakfasts. She purges. She begins on the peanut butter. After purging the entire contents of her recent buy at the grocery store she'd go out for lunch and it would begin again. After these episodes she'd be in the hospital from dehydration as often laxative and other diuretics would be used.

When she wasn't binging and purging Alisa would try to keep her diet to under 200 calories a day. She takes notes on every item, including "two peanuts" and the calories in relation to them.

All the women leave treatment looking much better. Alisa's skin is smoothed out and her eyes are less angry. Brittany is thinner but her skin is clear and her hair looks healthy. Polly's weight is in a healthy range for her height, though she is asked to leave for unruly behavior in a very strict environment. Shelly looks like a whole different girl, with clear skin and eyes.

But within a couple years the first of the four girls falls victim to suicide. Polly succumbs at the age of 33. Brittany continues to restrict and dies after completion of the film to anorexia. Alisa attempts suicide with diuretics and returns to Renfrew but goes on to live her life. Shelly lost 17 pounds after check out and went through shock therapy.

​One out of every seven people suffering from anorexia will die from the disorder. It has been written that when a person becomes anorexic they will be this way for the rest of their life whether or not they eat fine and seem fully recovered. But this doesn't mean they can't live a full and good life.